Headphones and headsets in which the hoop band contact pressure force is adjustable have long been known. Hereinafter the term hoop band contact pressure force is intended to denote that force with which the ear pads are pressed against the head when the headphones or headset is fitted. In typical configurations that force can be adjusted by the provision of a possible way of altering the geometry of the hoop band or the coupling between the hoop band and the ear pads.
U.S. Pat. No. 1,649,551 describes headphones in which a flexible, one-part head hoop band is connected at both ends to one of two ear pads by way of a respective adjustable rotary joint. The spacing between the two ear pads and thus the hoop band contact pressure force can be varied by adjustment of those rotary joints. It will be noted however that this approach does not allow comfortable operation and does not permit easy adjustability when the headphones are in place.
U.S. Pat. No. 3,447,160 discloses headphones in which a C-shaped spring integrated in a one-piece head hoop band is more or less greatly stressed by way of an adjusting screw mounted to the apex of the head hoop band, to adjust the hoop band contact pressure force. A disadvantage in this case however is the complicated structure as the hoop band must be in the form of a deformable hollow body. In addition the adjustment range in which the hoop band contact pressure force can be varied is relatively slight.
U.S. Pat. No. 4,783,822 describes headphones in which two of the ends of a two-part head hoop band can be displaced with a translatory movement relative to each other. In that way the spacing between the two ear pads can be varied to adjust the hoop band contact pressure force.